1. Field of the Invention
This invention relates to current mirrors.
2. Description of the Related Art
A conventional current mirror has an input or reference device, which is usually diode-connected, and an output device. For increased accuracy the diode connection may be replaced by an amplifier which senses the voltages on the output electrodes of the reference and output devices and provides an output to the control electrodes of the devices. Under some circumstances the output current may be incorrect because the circuit that feeds the reference device is usually imperfect. The output current of such a circuit may change if the voltage across it becomes too small. The amplifier attempts to force almost identical voltages on the output electrodes of the reference and output devices. If the output voltage of the current mirror approaches an extreme of the output voltage range, the current feeding the reference device may change substantially, and the output current will be incorrect. Furthermore, if at start-up the output voltage approaches the said extreme, the amplifier may force the output electrode of the reference device to a similar voltage, and the circuit may "lock-up" in this undesired state with no current flow.